This invention relates to reverberation tone generating apparatus, and more particularly, reverberation tone generating apparatus wherein a reverberation tone is formed by synthesizing a reverberation tone having irregular delay time and amplitude level and a reverberation tone having regular delay time and amplitude level.
In prior art apparatus for generating a reverberation tone with an electronic circuit, such analog delay element has been used as a BBD (bucket brigade device) or a CCD (charge coupled device). As illustrated in FIG. 1, such delay element includes a feedback loop FBL which feeds back a delayed output signal to the input of a delay circuit DC constituted by a BBD or the like. The delay circuit DC delays by a time DT a signal obtained by adding an input musical signal and the fed back signal and outputs the delayed signal.
With this delay circuit a reverberation tone can be obtained that manifests a regular impulse response determined by the delay time DT of the delay circuit DC and the gain g of the feedback loop FBL, as shown in FIG. 2.
The result of analysis of an actual reverberation tone produced in a concert hall shows that an initial reflected tone (echo) ECH reflected from wall surfaces or a floor surface and having irregular amplitude level and delay time appears firstly and thereafter a reverberation tone RV having regular amplitude level and reverberation time appears as shown by the inpulse response characteristic shown in FIG. 3. Consequently, with the delay circuit shown in FIG. 1 it is impossible to produce a natural reverberation tone obtained in a concert hall.
FIG. 4 shows another prior art circuit in which a plurality of delay circuits DC.sub.1 through DC.sub.n, whose delay times are randomly set, are connected in series, the levels of the outputs of respective delay circuits being independently controlled by level control circuits GC.sub.1 through GC.sub.n and then synthesized by a synthesizing circuit CC to obtain an initial reflected tone ECH and a reverberation tone RV havng impulse response characteristics as shown in FIG. 3.
However, in order to produce a reverberation tone rich in naturality with the circuit shown in FIG. 4, it is necessary to provide a large number of the delay circuits which not only increases the size of the apparatus but also is uneconomical.